1. Field of the Invention
The present invention relates to a blow molding device adapted to form a blow molded article from a thermoplastic synthetic resin, and more particularly, to a blow molding device adapted to form a blow molded article of which an outer wall is formed from a thermoplastic synthetic resin through blow molding and which has a built-in part in an interior thereof.
2. Description of Related Art
Conventionally, tubular blow molded articles, such as fuel tanks for use in motor vehicles, etc., have been formed of metal, but, in recent years, thermoplastic synthetic resins have been frequently used to form such tubular blow molded articles, because they can effect lightweight vehicle bodies, no rust is generated therein, and they can be readily formed into desired configurations.
In many cases, the tubular articles made of thermoplastic synthetic resins have been formed by the blow molding method, because tubular bodies can be readily formed. With the blow molding method, a parison of a molten thermoplastic synthetic resin formed into a cylindrical configuration is extruded from the upper side of a mold, and air is blown into the parison while the parison is being held with the mold, thereby forming the tubular bodies.
On the other hand, the blow molding method has been required to provide built-in parts such as valves, baffle plates adapted to restrain noise caused by the flowing of fuel, etc. in an interior of the blow molded article, such as the fuel tank.
Accordingly, in order to provide the built-in parts in the interior of the fuel tank, a device shown in FIGS. 1 through 4 has been used (see published Japanese patent application No. Hei 6-143396, for example.).
As shown in FIG. 1, a built-in part 10 is placed on a holding rod 12 before lowering a parison 14 in a blow mold 16, and the blow mold 16 is opened to position the built-in part 10 in an interior thereof. Next, the parison 14 is lowered with the blow mold 12 left open such that the built-in part 10 is positioned in the interior of the parison 14.
Then, as shown in FIG. 2, slide cores 18 are made to project from both sides of the blow mold 16 before the blow mold 16 is closed to press the parison 14 against side edges of the built-in part 10. As a result, the parison 14 can be fused to the side edges of the built-in part 10, because an interior surface of the parison 14 has not become solid.
Next, as shown in FIG. 3, the holding rod 12 is lowered, the blow mold 16 is closed, and the parison 14 is pushed with the slide cores 18 to hold the built-in part 10. And a blow pin 20 is pierced through the parison 14 to blow air from blowing means 22, thereby carrying out the blow molding.
And, as shown in FIG. 4, the parison 14 is pressed against a molding surface of the blow mold 12, which defines a cavity thereof, thereby forming a tubular body.
In order to continuously hold the built-in part 10 with the slide cores 18 from the time the blow mold 12 is opened, as shown in FIG. 2, until the blow mold 12 is closed, as shown in FIG. 3, the slide cores 18 have been required to retract gradually from the interior of the cavity with slide core driving means 24 according to the closing of the blow mold 16. To this end, the slide core driving means 24 must be provided separatedly from the blow mold 12, and consequently, the device costs and the maintenance costs increase.